Our hypothesis is that the immune system can be manipulated to control a limited systemic tumor burden remaining after surgical excision of colorectal cancers. Immunostimulation using an autologous tumor cell-BCG vaccine (active specific immunotherapy - ASI) will be studied as an adjunct to surgical resection in patients with colorectal cancer. The immunomodulating effect of low dose cyclophosphamide on the efficacy of the vaccine will also be studied. We will initiate a prospectively randomized, controlled trial (Phase III) in Dukes' B2 - C3 colorectal cancer patients to compare the disease free interval and survival in patients treated by A) surgical resection alone, B) surgical resection plus ASI, and C) surgical resection plus ASI preceded by cyclophosphamide. The three-armed trial will incorporate completion of a currently ongoing trial (A vs B). The continued translation of methods learned from experimental studies into carefully controlled clinical trials may provide a significant advance in the control of colorectal and other common malignant tumors.